OBDII Error Code P0107: Understanding and Troubleshooting a Low MAP Sensor Circuit

The OBDII error code P0107, often indicating “Manifold Absolute Pressure/Barometric Pressure Circuit Low Input,” is a common issue that can affect your vehicle’s performance. As an expert at autelfrance.com, specialized in automotive diagnostics and repair, we’re here to provide a comprehensive guide to understanding, diagnosing, and resolving this error.

Decoding P0107: Manifold Absolute Pressure Explained

P0107 is a diagnostic trouble code (DTC) that signals a problem within the Manifold Absolute Pressure (MAP) sensor circuit. The MAP sensor is a crucial component in your car’s engine management system. It’s designed to measure the pressure inside the intake manifold, providing vital data to the Powertrain Control Module (PCM).

The PCM supplies a 5-volt reference voltage to the MAP sensor. Inside the sensor, a resistor reacts to pressure changes in the manifold. This reaction modulates the voltage signal sent back to the PCM, typically ranging from 1 volt (high vacuum/low pressure) to 4.5 volts (low vacuum/high pressure, indicating engine load). This voltage signal is critical for the PCM to accurately calculate fuel delivery and ignition timing.

When the PCM detects that the voltage signal from the MAP sensor is abnormally low – specifically below 0.25 volts – it interprets this as a “Low Input” condition and sets the P0107 error code. This low voltage reading suggests a potential fault in the sensor, its circuit, or related components.

Recognizing the Symptoms of a P0107 Error

A P0107 error code can manifest in several noticeable symptoms that impact your vehicle’s driveability. Recognizing these symptoms early can aid in quicker diagnosis and repair. Common symptoms associated with a low MAP sensor signal include:

• Difficulty Starting: The engine may struggle to start, requiring extended cranking.
• Prolonged Cranking Times: The engine might crank for an unusually long duration before starting.
• Engine Sputtering or Misfiring: Irregular engine operation, including sputtering or misfires, can occur, especially during acceleration.
• Black Smoke from Exhaust: Excessive fuel in the combustion mixture due to incorrect MAP sensor readings can lead to black smoke.
• Reduced Fuel Efficiency: Inaccurate fuel delivery can result in poor gas mileage.
• Intermittent Engine Stalling: The engine may stall unexpectedly, particularly at idle or low speeds.
• Illuminated Malfunction Indicator Lamp (MIL): The check engine light will typically illuminate on the dashboard, signaling a detected issue.

Pinpointing the Causes of a P0107 Code

The P0107 error code can stem from various underlying issues. Identifying the root cause is essential for effective repair. Potential causes for a low MAP sensor signal circuit (P0107) include:

• Faulty MAP Sensor: The MAP sensor itself might be defective and providing inaccurate readings.
• Signal Circuit Issues: An open or short circuit in the signal wire between the MAP sensor and the PCM can disrupt signal transmission.
• 5 Volt Reference Circuit Problems: An open or short in the 5-volt reference wire supplying power to the MAP sensor can cause malfunction.
• Ground Circuit Faults: Issues with the ground circuit, such as an open or short, can impede proper sensor operation.
• PCM Malfunction: In rare cases, a faulty PCM could be the source of the problem, although this is less common.

Step-by-Step Troubleshooting for P0107

Diagnosing and resolving a P0107 error requires a systematic approach. Follow these troubleshooting steps to pinpoint and fix the issue:

1. Initial Voltage Check: With the ignition key turned to the “ON” position and the engine off, use a scan tool to monitor the MAP sensor voltage. A reading below 0.5 volts indicates a low signal condition, confirming the P0107 code’s indication.

2. 5 Volt Reference Verification: Turn the engine off and disconnect the MAP sensor connector. Using a Digital Volt-Ohm Meter (DVOM), check for the presence of 5 volts on the 5-volt reference circuit pin at the MAP sensor connector.

   • No 5 Volt Reference: If 5 volts are absent, check for the reference voltage at the PCM connector.
     • Voltage at PCM Connector: If 5 volts are present at the PCM connector but not at the MAP sensor connector, there’s an open circuit in the reference wire between the PCM and MAP sensor harness connector. Repair the open circuit.
     • No Voltage at PCM Connector: If 5 volts are missing at the PCM connector, investigate PCM power and ground circuits. Repair or replace PCM as necessary. (Note: In Chrysler vehicles, a shorted Crank sensor, Vehicle speed sensor, or other 5-volt reference sensors can cause a 5-volt reference short. Disconnect each sensor one by one until the 5-volt reference returns to identify the shorted sensor.)

3. Signal Circuit Test: If 5 volts are present at the MAP sensor connector, use a jumper wire to connect the 5-volt reference circuit pin to the signal circuit pin at the MAP sensor connector. Monitor the MAP voltage on the scan tool. It should now read between 4.5 and 5 volts.

   • Voltage within Range: If the voltage is within the expected range, replace the MAP sensor, as it is likely faulty.
   • Voltage Still Low: If the voltage remains low, there’s likely an open or short circuit in the signal wire. Repair the signal circuit wiring and re-check.

4. Wiggle Test: If wiring appears intact, perform a wiggle test. Start the engine and gently wiggle the MAP sensor harness and connector. Lightly tap on the MAP sensor itself. Observe the scan tool for any fluctuations in voltage or changes in engine speed. Repair or replace the connector, harness, or sensor as indicated by the test.

5. Vacuum Test: If the wiggle test yields no results, use a vacuum pump (or carefully use your mouth) to apply vacuum to the MAP sensor vacuum port. As vacuum is applied, the voltage reading on the scan tool should decrease. With no vacuum applied, the MAP sensor should read approximately 4.5 volts. If there is no change in the MAP sensor reading with vacuum application, the MAP sensor is likely defective and needs replacement.

By following these steps, you can effectively diagnose and address the P0107 OBDII error code. Remember to always prioritize safety when working on your vehicle and consult a professional mechanic if you are unsure about any step. For advanced diagnostics and efficient repairs, consider utilizing professional tools from Autel, designed to streamline the troubleshooting process for automotive technicians and enthusiasts alike.

Understanding OBDII error codes like P0107 is the first step towards maintaining your vehicle’s optimal performance. With the right knowledge and tools, you can tackle common automotive issues and ensure a smooth and efficient driving experience.